Most of the whole blood collected from volunteer donors today is not itself stored and used for transfusion. Instead, the whole blood is separated into its clinically proven components (typically red blood cells, platelets, and plasma), which are themselves individually stored and used to treat a multiplicity of specific conditions and diseased states. For example, the red blood cell component is used to treat anemia; the concentrated platelet component is used to control thrombocytopenic bleeding: and the platelet-poor plasma component is used as a volume expander or as a source of Clotting Factor VIII for the treatment of hemophilia.
Systems composed of multiple, interconnected plastic bags have met widespread use and acceptance in the collection, processing and storage of these blood components. In the United States, these multiple blood bag systems are subject to regulation by the government. For example, the plastic materials from which the bags and tubing are made must be approved by the government. In addition, the maximum storage periods for the blood components collected in these systems are prescribed by regulation.
In the United States, whole blood components collected in a nonsterile, or "open", system (i.e. one that is open to communication with the atmosphere) must, under governmental regulations, be transfused within twenty-four hours. However, when whole blood components are collected in a sterile, or "closed", system (i.e., one that is closed to communication with the atmosphere) the red blood cells can be stored upwards to forty-two days (depending upon the type of anticoagulant and storage medium used); the platelet concentrate can be stored upwards to five days (depending upon the type of storage container); and the platelet-poor plasma may be frozen and stored for even longer periods. Conventional systems of multiple, interconnected plastic bags have met with widespread acceptance, because these systems can reliably provide the desired sterile, "closed" environment for blood collection and processing, thereby assuring the maximum available storage periods.
In collecting whole blood components for transfusion, it is desirable to minimize the presence of impurities or other materials that may cause undesired side effects in the recipient. For example, because of possible febrile reactions, it is generally considered desirable to transfuse red blood cell substantially free of the white blood cell components, particularly for recipients who undergo frequent transfusions.
One way to remove white blood cells is by washing the red blood cells with saline. This technique is time consuming and inefficient, as it can reduce the number of red blood cells available for transfusion. The washing process also exposes the red blood cells to communication with the atmosphere, and thereby constitutes a "non-sterile" entry into the storage system. Once a non-sterile entry is made in a previously closed system, the system is considered "opened", and transfusion must occur within twenty-four hours, regardless of the manner in which the blood was collected and processed in the first place. In the United States, an entry into a blood collection system that presents the probability of non-sterility that exceeds one in a million is generally considered to constitute a "non-sterile" entry.
Another way to remove white blood cells is by filtration. Systems and methods for accomplishing this within the context of conventional multiple blood bag configurations are described in Wisdom U.S. Pat. Nos. 4,596,657 and 4,767,541, as well as in Carmen et al U.S. Pat. Nos. 4,810,378 and 4,855,063. In these arrangements, an inline white blood cell filtration device is used. The filtration can thereby be accomplished in a closed system. However, in these arrangements, the filtration process ultimately results in transferring the red blood cells out of the primary blood collection bag and into another bag for storage. Therefore, the filtration process requires both a primary blood collection bag and a second blood storage bag, both of which are subject to relatively stringent governmental regulations relating to blood containers.
Therefore, a need still exists for systems and methods for removing undesired matter from blood components prior to transfusion or storage in a way that lends itself to use in closed system environments, but which do not necessarily require the use of additional blood storage containers that are subject to stringent governmental regulations.